Species which are spread over a wide area or in different ecological conditions are said to be cosmopolitan. Some of them, called endemics are restricted to their distribution to a small region..
The term 'endemism' was coined by A.P. de candolle
(1855) for the distribution of an organism in a limited geographical area
The phenomenon of
restricted distribution of living organisms associated with some geographical
or ecological factors is called endemism.
Among endemics, some
species exhibit very localized distribution such as in small islands or
mountain peaks and are called local endemics.
Some species may show
restricted distribution but cover large areas in course of time. This is called
expanding or progressive endemics.
Endemic families are the ones which grow
only in a particle province of a country or continent. For example Cerciphyllaceae
represented by two species in China. Davidiaceae is represented in Asia,
Arachiaceae and Bruniaceae are represented by three species each
in South Africa.
There are following
two types of endemics –
1. Paleo endemic
or epibiotic or relics: these endemics are supposed to have been the remnants
of a once widely distributed taxon in the past, e.g., Gingo biloba, Sequoia
semipervivens.
2. Neoendemics or micro endemics :
these endemic taxa are supposed to have evolved only during the recent times
and did not have sufficient time to extend their range of distribution.
About 4,900 species of flowering plants or 33% of the
recorded flora are endemic to the country These are distributed over 141 genera
belonging to 47 families. These are concentrated in the floristically rich
areas of North-East India, the Western Ghats, North-West Himalaya and the
Andaman & Nicobar Islands.
The Western Ghats and the Eastern Himalaya are
reported to have 1,600 and 3,500 species of flowering plants, respectively.
These areas constitute two of the 18 hot spots identified in the world. It is
estimated that 62% of the known amphibian species are endemic lo India of which
majority occur in Western Ghats. Nearly 50% of the lizards found in India are
endemic
Endemic Species of India:
Rhododendron (Ericaceae),
Beaumontia grandiflora (Apocynaceae),
Eleusine coracana (Poaceae),
Caryota urena (Arecaceae),
Aegle marmelos (Rutaceae),
Crotolaria juncea (Fabaceae),
Ficus religiosa (Moraceae), and
Seasamum indicum (Pedaliaceae).
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